There are two conventional methods of radial scanning ultrasonic endoscopes, the electronic scanning method that performs electronic scans and the mechanical scanning method that performs mechanical scans. In the ultrasonic endoscopes of the electronic scanning method, the configuration is generally employed in which the ultrasonic transducer formed in a cylindrical shape for performing the radial scan and the endoscopic observation and endo-therapy units for performing endoscopic image observation are arranged in very close proximity to each other and are fixed as one piece, and a plurality of flexible printed circuit (FPC) boards are used as cables for transmitting electric signals to and from the ultrasonic transducer.
In addition, a plurality of FPC boards connected to the transducer elements are arranged in such a manner that an arch is formed by the plurality of FPC boards in order to avoid being close to the endoscopic observation and endo-therapy units such as its instrument channel port and the like, and thereafter the plurality of FPC boards are connected to signal cables (coaxial cables) at a spot closer to the proximal end than the bending section of the endoscope (on the side of the control section of the ultrasonic endoscope body) (see Patent Document 1, for example).
In the ultrasonic endoscopes of the mechanical scanning method, a scan is performed by turning one ultrasonic transducer in the insertion axis direction using an electric motor or the like provided at the proximal end. Accordingly, the ultrasonic transducer is attached by means of a shaft bearing structure such as ball bearings provided in the vicinity of the ultrasonic transducer (see Patent Document 2, for example).    Patent Document 1    Japanese Patent Application Publication No. 2001-314406    Patent Document 2    Japanese Patent Application Publication No. 2-116358